In recent years, solid state drives (SSDs) configured with a plurality of NAND flash memories and a controller have been used in storage systems, server devices, laptop PCs, and the like. In the NAND flash memory, there is an upper limit in the number of erasures, and the number of erasures is known to be a factor determining the lifespan of an SSD.
PTL 1 discloses a semiconductor memory device configured with a NAND flash memory, a non-volatile buffer memory, and a memory control unit. Write data input to the semiconductor memory device is first written in a non-volatile buffer memory and then written in the NAND flash memory.
PTL 2 discloses a semiconductor memory device configured with a non-volatile memory, a RAM, and a controller. An address translation table is stored in the non-volatile memory, and a part of the address translation table is stored in the RAM.